1. Field of the Invention
The present invention relates to a method of delivering reaction gases during deposition of a predetermined layer onto a substrate with two or more mutually-reactive reaction gases, and a shower head used to introduce the reaction gases.
2. Description of the Related Art
Physical vapor deposition (PVD, also referred to as xe2x80x9csputteringxe2x80x9d), chemical vapor deposition (CVD), atomic layer deposition (ALD), and pulsed CVD (PCVD, the details of which will be described later) can be used to form a predetermined layer by depositing a vapor material on a substrate. When a predetermined layer is formed by conventional vapor deposition methods, source gases (reaction gas) are generally provided by a shower head installed at the upper portion of a reaction chamber.
FIGS. 1 and 2 show a mixing-type shower head. Here, first and second reaction gases enter into a shower head 10 at the same time or at different times, according to the opening or closing action of valves 16, via intakes 12 and 14, respectively. The first and second reaction gases are mixed in the shower head 10, exit through outlets 18 on the bottom surface of the shower head 10, and are deposited on a substrate (not shown) loaded in a reaction chamber. However, in the mixing-type shower head 10 having such a configuration, the first and second reaction gases, particularly if they are mutually reactive, react with each other and form particles, which are deposited within the shower head 10. Therefore, the shower head is easily contaminated.
FIGS. 3 and 4 show a separative type shower head 30, for separately providing first and second reaction gases, to solve the above problem. Referring to FIGS. 3 and 4, different passages are provided to prevent the first and second reaction gases from reacting with each other within the shower head 30, such that the first and second reaction gases are discharged respectively via separate sets of interspersed outlets 38 and 40. However, when PCVD is performed using the separative type shower head 30, the first reaction gas and other reactants remaining within the reaction chamber flow backward and into the passage for the second reaction gas, because there is no downward flow at that point coming from the passage for the second reaction gas. Then, when the second reaction gas is delivered, it reacts with the first gas and other reactants, thereby producing contaminating particles. Likewise, the same thing occurs in the passage for the first reaction gas, which becomes contaminated with the second reaction gas when only the second reaction gas is flowing.
Meanwhile, during introduction of the first and second reaction gases, a predetermined amount of inert carrier gas can be used to help carry the reaction gases. Accordingly, the backward flow of a reaction gas through a passage for the other reaction gas which is not being delivered is prevented by continuously delivering the inert carrier gas independently of the delivery of the reaction gas, or by purging the reaction gas remaining within the shower head and the reaction chamber by increasing the flow rate of a purge gas. In the case where the carrier gas is continuously delivered as described above, the carrier gas acts as the purge gas when neither of the two reaction gases is being delivered.
However, the continuous delivery of the carrier gas and the increase in the flow rate of the purge gas cause a reaction gas adsorbed on the substrate to be purged, so that the deposition rate of a film is significantly decreased. For example, when a TiN film is deposited by using the shower head shown in FIGS. 3 and 4, the relationship between the flow rate of a purge gas and the deposition rate of the TiN film is shown in FIG. 5. Here, TiCl4 is used as a first reaction gas, NH3 is used as a second reaction gas, and Ar is used as a purge gas. As can be seen from FIG. 5, when the flow rate of purge gas increases to over 200 sccm, the deposition rate of the TiN film falls below 10 xc3x85/min. Therefore, the conventional gas delivery method is not appropriate for a practical mass production process. According to several experiments, it becomes evident that setting the flow rate of purge gas to over about 500 sccm prevents contaminating particles from being produced. However, it can be seen that setting the flow rate of the purge gas to over 500 sccm greatly reduces the speed of growth of the TiN film.
To solve the above problems, it is an object of the present invention to provide a method of delivering gas whereby problems of both an increase in contaminating particles and a reduction in deposition rate can be solved, and to provide a shower head appropriate for the gas delivery method.
Accordingly, to achieve the first object, the present invention provides a gas delivery method in which a first reaction gas is delivered toward the edge of the substrate, and the other reaction gases are delivered toward the central portion of the substrate, each of the reaction gases being delivered via independent gas outlets to prevent the reaction gases from being mixed. Here, the predetermined film can be deposited by atomic layer deposition (ALD) or pulsed chemical vapor deposition (PCVD).
The other reaction gases include second and third reaction gases each reactive to the first reaction gas, and the second and third reaction gases can be delivered simultaneously with the first reaction gas. The second and third reaction gases can be simultaneously delivered via the same gas outlet to be mixed with each other or alternately delivered via the same gas outlet at different times to prevent the two reaction gases from being mixed. Alternatively, the second and third reaction gases can be delivered via independent gas outlets, respectively, to prevent the two reaction gases from being- mixed.
According to another embodiment of the present invention, there is provided a gas delivery method including: delivering the first reaction gas toward the edge of the substrate for a designated period of time; purging the reaction gas remaining within the reaction chamber while blocking the inflow of the first reaction gas; delivering the second reaction gas toward the central portion of the substrate for a designated period of time; and purging the reaction gas remaining within the reaction chamber while blocking the inflow of the second reaction gas.
In the steps of delivering the first reaction gas and the second reaction gas, each of the first and second reaction gases is delivered together with a carrier gas in order to smoothly supply the first and second reaction gases. The reaction chamber is purged by continuously delivering only the carrier gas while blocking the first and second reaction gases during each of the purging steps. Also, the first reaction gas delivering step, the purging step, the second reaction gas delivering step, and the purging step can be repeated to deposit the material to a desired thickness.
The shower head appropriate for carrying out the above method is installed at the upper portion of a reaction chamber in which a substrate is seated on the lower portion. The shower head has a gas supply line formed on the upper surface of the shower head for receiving a first reaction gas from a supply source of the first reaction gas; gas supply lines formed on the upper surface of the shower head for receiving other reaction gases from a supply source of the other reaction gases; a plurality of outlets for the first reaction gas formed along the edge of the lower surface of the shower head for discharging the first reaction gas; a plurality of outlets for each of the other reaction gases formed on the central portion of the lower surface of the shower head, for discharging the other reaction gases; a gas passage formed within the body of the shower head, for connecting the gas supply line for the first reaction gas to the plurality of outlets for the first reaction gas; and gas passages formed independently of the gas passage for the first reaction gas within the body of the shower head, for connecting the supply lines for the other reaction gases to the plurality of outlets for each of the other reaction gases.
Here, the plurality of outlets for the first reaction gas can be extended further downward toward the substrate than the plurality of outlets for each of the other reaction gases such that the plurality of outlets for the first reaction gas are closer to the substrate installed in the chamber than the plurality of outlets for each of the other reaction gases when the shower head is installed in the upper portion of the reaction chamber.
According to the present invention, one of the mutually-reactive reaction gases is delivered toward the edges of a substrate, and the others are delivered independently toward the center of the substrate. Thus, generation of contaminating particles within a shower head and a reaction chamber can be prevented, and a high deposition rate can be obtained.